Introduction

I am currently writing a series on a
recent article by Sean
Carroll. This will take me several posts to respond to it fully, so I am going one section at
a time. My previous post
gave an introduction to the topic, and covered Carroll's own introduction. In this post, I
will discuss the first section of the article, entitled "What Does Why Mean?"

In this article, Carroll is focusing on the "fundamental question of metaphysics." If science and philosophy are largely concerned with questions of how things are, but the more fundamental question is why things are. But before we answer this question, we need to
ask what we mean by Why, and what sort of answers we might expect.
The purpose of this section is to address that issue.

Carroll's conclusion in this section is that there are five possible answers to this
question, and I actually agree with him on this point, so I will come to it first.
His five possibilities are:

Creation. There is something outside reality which brings it into existence,
and/or sustains it. This is often identified with God or some sort of necessary being.

Metaverse. Reality is just one member of a wider series of structures.
For example, one might have pocket universes emerging from a larger structure, or a
bouncing universe where one universe dies and then another begins, stretching back to
infinity, although Carroll intends his concept to be more profound than this. This wider
structure will be similar to our own reality (for example governed by similar rules, so
it is distinct from the idea of a creator), but larger and at a more fundamental level.

Principle. Reality is the way it is because of some underlying principle, perhaps simplicity or beauty.

Coherence. The concept of "nothingness" is incoherent, so anything except a
universe consisting of something is non-viable.

Brute Fact. Reality is the way it is, and that's it. Eventually, the chain
of explanation will reach a point where we can't go any further. The is no underlying
reason why that terminus has to be what it is -- it could be different -- but it just
happens to be that way, and we have to live with it.

My main quibble with all of this is Carroll's use of the word reality here as a synonym for the universe. His definition of the universe was:

I'm using "universe" here to refer to the entirety of physical reality. No
judgement is implied about whether things other than physical reality
can be usefully said to exist.

If so, there is a distinction we need to make between physical reality and
reality. The two can only be equated if physical reality is all that there is.
However, this is something that would be disputed by those who hold to a creator,
Professor Carroll's first option. These people would claim that God is part of reality, but
not physical reality. This issue be avoided by replacing reality with
physical reality in all of Carroll's five possible answers above.

The second thing I want to note immediately is that there is a great deal of similarity
between the Creator and Brute Fact options. Both of them postulate that the
chain of causality terminates at some point. The difference is in what they believe about
the nature of that point of termination. Those who advocate a Creator will say that He (or
It)
can only be the way He (or It) is. The classic example of this is the being of pure
actuality
in the Thomist tradition. The Potentia list the possible states into which a being can
change into, similar to how an electron orbiting an atom has different energy levels or
eigenstates of the Hamiltonian. These energy levels would represent the different possible
potentia. In a classical Aristotelian metaphysics, only one of these can be occupied at a
given time, and that state exists actually. The remaining states can be said to exist
potentially, since there is a possibility that the electron will be excited into one of
them,
or decay into a lower energy state. God, being a being of pure actuality, has no potentia.
He cannot be other than as He is (and is incapable of change). Thus while it is necessary
and possible to explain why the electron is in that particular eigenstate rather than
another, we cannot sensibly ask why God is as He is because there are no other options.

In these terms, the brute fact approach states that the sequence of explanations ends with
something that is a mixture of potentiality and actuality. It could be something else,
but happens not to be, and there is no underlying reason why it is in the state it is. Of
course, this precise terminology can only directly be applied if the sequence of
explanations ends with some sort of being, rather than (say) some abstract principle such
as a law of quantum gravity. But even in the case of the abstract principle, we can still
invoke a similar principle. There are numerous different ways the law of gravity could exhibit itself (for example, with different values of the ratio between the Planck mass and
the Higgs Mass); one of them is actual, and the others are potential.

A second quibble is that Proffessor Carroll doesn't mention a sixth possibility,
namely an infinite regression of explanations. Presumably that means that he believes
the arguments against this are sufficiently strong that the possibility is not worth
mentioning. Since I agree with him that the arguments against this view are strong, I won't
discuss it further. But some will be disappointed to see its omission.

Mechanism and Purpose

So having started with Carroll's conclusion, and broadly accepted it,
I ought to go back to the start of this section and point out where I have issues as he
guides us to that conclusion. The first one arises in his very first paragraph. Since the time
of Aristotle, philosophers have tried to
understand what the possible senses there could be for
why something is.

For our limited purposes here, it should suffice to distinguish between how the universe came to be and what mechanism (if any) might have brought it into being – corresponding roughly to Aristotle’s efficient cause – and the reason why (if any) it exists – corresponding to the final cause. Aristotle conceived of final causes teleologically, as ends or purposes. Here we’re being a little broader, expanding the category to include anything that would qualify as a "reason why." Let us label these notions mechanisms
and reasons for short.

So Carroll manages to get both the efficient cause and the final cause wrong in two
consecutive sentences. Firstly, the efficient cause is not a mechanism. It is a substance.
In a weak interaction event, an electron decays into a W- Boson and anti-
neutrino. The mechanism is whatever it is that lies behind the weak interaction. The
efficient cause of both the Boson and the anti-neutrino is the initial electron. And this
is always the case: an efficient cause is always a being, such as an electron, quark,
or protein molecule. This is a key difference between classical theories of causality and
modern theories of causality, which do look for a mechanism or event behind the change.

Next we have the final cause, which Carroll denotes as an end or purpose. End is not
actually too unreasonable, although we have to qualify it a bit. The final cause once again
points to another physical state or potentia. So, among the final causes of the electron
are the W- Boson and anti-
neutrino (with the particular energy, momentum and spin from that particular decay). So we
can correctly relate the concept with an end, but only if we mean
the right thing by end. Equating final causality with purpose has a
long history, so Professor Carroll shouldn't perhaps be criticised too much for making
the same mistake. The definition was, I think, first proposed by the Stoics including
Cicero, and entered
Western European thought during the Renaissance. So if you are discussing post-Renaissance
thought, then this definition is reasonable. But Carroll is referencing Aristotle here, and
(no doubt
somebody will correct me), I believe that among the major Aristotelian philosophers, this
definition of final causality was rarely used. Of course, Aquinas argued that because of
final causality, there had to be a guiding purpose behind matter (which he equated with God), but that is arguing from the Aristotelian principle to the Will of God, not equating
final causality with purpose. He could hardly have been arguing "Because there is purpose in nature, there has to be a purpose guiding it," since that is clearly circular.

Finally, after all his good work saying that there are different ways in which one could answer the question "Why," Carroll decides to lump them all together under his own definition of final causality. Oh well.

In my previous post, I spent some time describing the difference between deism and theism.
And this is one example of why I had to do that. Mechanisms and reasons are
categories that are used in the modern philosophy of physics, which underlies deism. They
are not categories that a classical philosopher or classical theologian would find useful,
at least not in the sense that Carroll means them. Of course, that leaves the question of
whether modern philosophy or classical philosophy are best used to describe modern physics,
but that is another topic. I discussed earlier how the Aristotelian concepts of efficient
and final causality fit in with one quantum physical process, and we can also see how
the classical notion of mechanism doesn't fit in so well.

Carroll is searching for the answer to the question of what mechanism brought the universe
into existence, a scientific question that ought to be informed by the best of modern
science. I agree. But then asking the reason is different. Aristotle believed that final
causality is a fundamental feature of reality. Modern Physics disagrees.
Rather than describing things in terms of effects and causes, it states that the universe
is described by patterns, the laws of physics. These relate different conditions at different times and places to
each other, "typically by differential equations." Every "Why" question is reducible to
those laws and the initial conditions. The laws are a description of patterns, a Humean account of the laws of physics.

But of course, Aristotle's vision of final causality is not what Carroll described it as.
And the
disagreement was promoted when Galileo and Newton were King, and we now know that they were
both fundamentally wrong about physics. So Carroll is comparing something that
was not what Aristotle proposed against an incorrect physics. This doesn't really tell us
much of use at all, either about Aristotle or about physics or about reality. Crucially,
contemporary physics no longer makes use of differential equations in the same sense that
Newton did. Newton's laws of motion relates the location and time of the particles in the
universe, and their interactions, with a differential equation. Plug in the initial
conditions, solve the equations, and you can work out what will happen in the future. But
that was disposed with a century ago.

Quantum mechanics moves a step away from this. Here we have a single particle wavefunction
which evolves according to a differential equation, except when we take measurements.
What this wavefunction represents is an unsolved philosophical problem, but not one that
need concern us here. The evolution of the wavefunction is deterministic, but that is not
the whole story, because it only describes the probability amplitude that a particle is
in a given state, not what is actually happening with the particle (if the question of
something actually happening makes sense in quantum mechanics). But the process of
solving problems in quantum mechanics is similar to that in classical mechanics: it
involves solving a lot of differential equations.

But, when we get to quantum field theory, the merger between special relativity and
quantum physics, the evolution of matter is no longer described by a differential equation.
Instead we have integrals over functions or operators. The Feynman diagram expansion
(while only a guide, since it describes unphysical unrenormalised particles) is a good
picture to have in mind. We have particles decaying into other particles, particles
absorbing other particles. Each coherent route between an initial and final state is
possible. Each one carries a certain amplitude. To get the final probability for a particular final state, we need to add up each of these amplitudes, and square it.
What this means is that the old view of physical laws, as outlined by Professor Carroll,
is no longer accurate. We are left with something far closer to Aristotle's vision of
causes and effects. The difference is that we are now able to calculate the amplitude
for each decay channel, while Aristotle could only list them. This is significant because
metaphysics should meet with the most fundamental physics, not approximations to it. We
have no reason to suspect that a theory unifying gravity with the standard model will be
any different in this regard from the standard model.

But Professor Carroll's problems are deeper than this. He both wants to use the laws as
an answer to the "why" question, and to have them as Humean descriptions of patterns. But
that won't work, because a description of a pattern doesn't explain anything. It is a bit
like asking "Why did that apple fall from the tree?" "Because of the law of gravity." "What
is the law of gravity?" "It is a description of the observation that every apple falls after detaching from a tree." That is just circular. It hasn't explained anything. Nor
does it give us any confidence that such laws work or would continue to work, because they
are not linked to nature.

I would also agree that the laws of physics are a description, but a description of
something that is inherent within nature. This could be a description of the ways in which
particles interact with each other (the final causes), or, at a deeper level, a description
of how God sustains the universe in accordance with its
created nature. The laws of physics describe interactions between different beings.
Therefore they cannot be fundamental; the notion of the beings themselves has to come first
(because you can't describe an interaction before you define what it is that interacts),
and the laws are either contained within that notion or follow from it.

It is certainly true that fundamental physical law is mostly described in terms of
symmetries of the Lagrangian. But we have to ask why those symmetries in particular are
satisfied. A call to symmetry is only a description of something that constrains the
mathematical form of the description of the interactions between two beings. As, indeed,
is a reference to locality, which is just as important in modern physics as a source of
conservation laws. In classical physics, the conservation of energy and momentum arise as
a consequence of local symmetries of the Lagrangian. In quantum physics, they arise
because the Lagrangian is local, and only contains interactions at the same point in
space-time.

Cause and effect

Carroll's argument in this section is that cause and effect language is no longer part of
fundamental physics (although it might emerge at higher levels of physics). He wants to
use this to say that it is pointless to think about the origin of the universe in terms
of a cause. However, the reason why language of causality was removed from physics research
is that it is not something that is easily representable mathematically. That doesn't mean
that it isn't there, but that it is something we have to induce from looking at the
structure of physical processes. When we talk about causes we mean that one state is destroyed and another created, and there is a relation between those two acts.
When I see the Hamiltonian of quantum field theory,
constructed from various creation and annihilation operators, I see one physical state
being annihilated and some others created at the same place in space and time. This is a
cause and effect process. That physicists don't usually use the language of cause and
effect to describe this doesn't change that.

I would agree with Carroll that it is wrong to apply the principle of causality to the
level of the universe, but for a different reason. Efficient and final causality apply to
individual beings, and the universe isn't an individual being. But that doesn't mean that
the idea of efficient causality and final causality aren't relevant for the question of
whether there is something rather than nothing. We still have a chain of efficient causes.
That chain must either continue indefinitely or terminate with something. We can ask,
if it terminates, then what is the nature of the being at the end of it, and whether all
such chains of causality terminate with the same being.

While we don’t currently know the once-and-for-all laws of nature, nothing
that we do currently understand about physics implies any necessary obstacle to thinking
of the universe as a fully law-abiding, self-contained system. In this case, there would be
no such thing as the "cause" or "reason why" the universe exists.

This statement, to my mind is a bit bold. Of course, one could argue that the beginning of
the universe points to something outside. Or a cosmological argument based on efficient
causality. One could also add that nothing implies that
the universe is a fully law abiding, self-contained system. One has to ask why those laws
are obeyed, and what it is about matter that makes it only decay in such a way that
momentum or electric charge are conserved (and calling on symmetry and locality principles
doesn't help: one still has to explain why the action has those symmetries and is local,
and why an action or Hamiltonian operator is useful in understanding how matter evolves).

I will also mention the indeterminacy
of physics as another reason for thinking that the universe is not self-contained. The
interpretations of probability which I find most reasonable, and which best
fit what we do in quantum physics, treat a probability in itself as a measure of
uncertainty, and probability theory as an extension to logic which deals with things that
are uncertain. Thus we only need to resort to probabilities if some facts aren't known.
If everything was known, we would be certain. Since we are uncertain about some details,
we have to use probability.
Quantum theory is indeterminate, meaning that one cannot make precise predictions even with
a complete knowledge of the present state of the universe. One can only express things in
terms of probabilities (or, more specifically, probability amplitudes). This suggests that
even with a complete knowledge of the universe, some facts are missing. Which
suggests that the universe is not self-contained. Are arguments of this sort completely
solid? Well, there are some assumptions I made that can be challenged. But thinking along
these lines
still casts doubt on Professor Carroll's assertion that there are no obstacles to thinking
that the universe is self-contained. We have to carefully define what is meant by
self-contained. Certainly the definition used in classical physics, which stated
that every event had a full in-universe explanation, cannot be sustained, on any
interpretation of the meaning of probability. So presumably, Professor Carroll means
something else by the term. It would be nice to know what it is.

And that is before we run into fifth way type arguments (not the argument from design,
but an argument from final causality). We have to ask why brute lumps of matter should
have a tendency towards certain decay channels and not others. To turn to the laws of
physics to answer this question isn't an answer: the laws describe what happens, but don't
explain it. To express this in terms
of the underlying symmetries is not answering the question, just rephrasing it. Yet the
behaviour of matter seems to be wholly rational, which suggests that there is an
explanation. But one that goes beyond the scope of physics, and thus physical reality.

One can also try to explain things by appealing to deeper principles. So, perhaps, once
we come up with a complete understanding of physics, it might turn out to be the
simplest possible universe, or the most symmetric, or so on. As Professor Carroll notes,
however, we would still need to explain why that principle held.

So then we come to the idea which Professor Carroll attributes to Leibniz that there is
explanatory regression which terminates with a necessary being. This is a point where no
further explanation is possible, because whatever the terminating principle is, it
couldn't be other than what it is. This has the advantage that it ties everything up
neatly. It is the solution to the problem that most theists adopt (albeit that they might
not express it in precisely these terms).

However, I should make one observation here: there is a difference between a necessary
being and a logically necessary being. A necessary being is the opposite of a contingent
being. A contingent being is one which could in principle have an explanation outside
itself for its existence and its present state (for a physical system, which eigenstate
of the Hamiltonian is actual). A necessary being is thus one which cannot have such an
explanation outside itself even in principle. Usually this is taken to mean that it could not be in any
state other than the one that it is currently in. The reason why it is in that particular
state is that it can't by its nature be in a different one. The second possible definition
is the logically necessary being. This is something whose non-existence in its
current state would be a logical contradiction. The two definitions are not equivalent;
one can describe necessary beings which aren't logically necessary
beings. For example, Thomas Aquinas' conception of God is necessary but
not logically necessary. It is not completely clear which of these definitions
Carroll is using. In the
section I am discussing in this post, he contrasts the idea of a necessary being
against a brute fact, which implies the first definition (a brute fact is a contingent
being which terminates a chain of explanations). Later on, in section 3, where he
presents arguments against the idea of a necessary being, he seems to adopt the second
definition. But I will get to that in due course.

Conclusion

So, I have reached the end of Carroll's first non-introductory section, where he discusses the meaning of the word Why and what possible answers we might give to the question why there is something rather than nothing. His final list of possible answers is
something I can accept, and since that is mainly what he takes from this section, I'm
vaguely with him so far. But he has also sowed the seeds of a few problems that will come back
to haunt him later. He made some minor mistakes in his understanding of classical
philosophy, and that has caused him to commit to one particular view of the philosophy
of science. He describes things in terms of mechanisms and reasons.
However,
it is not clear that his philosophy of science is correct. It is not what a classical
philosopher or classical theist would accept. Although popular today,
and the philosophy that drove the Galilean revolution, his idea that physics reduces to
laws which are described in terms of differential equations is now out of date.
His assertion that the universe is self contained is somewhat begging the question, and
there are reasons given the indetermancy of physics to suggest that it isn't so.
In Quantum
Field theory, it is somewhat different. But I will discuss that in more detail when I come
to his section 3. He is also a bit sloppy with some of his key definitions. At one point,
he equates the universe with physical reality, and the next with the whole of
reality. At one point, he defines a necessary being by contrasting it against a brute fact,
but later defines it as something that is logically necessary. So we are already starting
to see a few issues arising in his argument.

Next time, we move onto the question of what we mean by something and
nothing. It might be a few weeks before I can post again; I have a deadline looming,
and am a bit behind schedule in preparing for it. But the post will come when I am able to.

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